wtf/MessageQueue.h

   1 /*
   2  * Copyright (C) 2008 Apple Inc. All rights reserved.
   3  * Copyright (C) 2009 Google Inc. All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * 1.  Redistributions of source code must retain the above copyright
  10  *     notice, this list of conditions and the following disclaimer.
  11  * 2.  Redistributions in binary form must reproduce the above copyright
  12  *     notice, this list of conditions and the following disclaimer in the
  13  *     documentation and/or other materials provided with the distribution.
  14  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  15  *     its contributors may be used to endorse or promote products derived
  16  *     from this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  21  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  24  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  25  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29
  30 #ifndef MessageQueue_h
  31 #define MessageQueue_h
  32
  33 #include <limits>
  34 #include <wtf/Assertions.h>
  35 #include <wtf/Deque.h>
  36 #include <wtf/Noncopyable.h>
  37 #include <wtf/Threading.h>
  38
  39 namespace WTF {
  40
  41     enum MessageQueueWaitResult {
  42         MessageQueueTerminated,       // Queue was destroyed while waiting for message.
  43         MessageQueueTimeout,          // Timeout was specified and it expired.
  44         MessageQueueMessageReceived,  // A message was successfully received and returned.
  45     };
  46
  47     template<typename DataType>
  48     class MessageQueue : Noncopyable {
  49     public:
  50         MessageQueue() : m_killed(false) { }
  51
  52         void append(const DataType&);
  53         bool appendAndCheckEmpty(const DataType&);
  54         void prepend(const DataType&);
  55         bool waitForMessage(DataType&);
  56         template<typename Predicate>
  57         MessageQueueWaitResult waitForMessageFilteredWithTimeout(DataType&, Predicate&, double absoluteTime);
  58         void kill();
  59
  60         bool tryGetMessage(DataType&);
  61         bool killed() const;
  62
  63         // The result of isEmpty() is only valid if no other thread is manipulating the queue at the same time.
  64         bool isEmpty();
  65
  66         static double infiniteTime() { return std::numeric_limits<double>::max(); }
  67
  68     private:
  69         static bool alwaysTruePredicate(DataType&) { return true; }
  70
  71         mutable Mutex m_mutex;
  72         ThreadCondition m_condition;
  73         Deque<DataType> m_queue;
  74         bool m_killed;
  75     };
  76
  77     template<typename DataType>
  78     inline void MessageQueue<DataType>::append(const DataType& message)
  79     {
  80         MutexLocker lock(m_mutex);
  81         m_queue.append(message);
  82         m_condition.signal();
  83     }
  84
  85     // Returns true if the queue was empty before the item was added.
  86     template<typename DataType>
  87     inline bool MessageQueue<DataType>::appendAndCheckEmpty(const DataType& message)
  88     {
  89         MutexLocker lock(m_mutex);
  90         bool wasEmpty = m_queue.isEmpty();
  91         m_queue.append(message);
  92         m_condition.signal();
  93         return wasEmpty;
  94     }
  95
  96     template<typename DataType>
  97     inline void MessageQueue<DataType>::prepend(const DataType& message)
  98     {
  99         MutexLocker lock(m_mutex);
 100         m_queue.prepend(message);
 101         m_condition.signal();
 102     }
 103
 104     template<typename DataType>
 105     inline bool MessageQueue<DataType>::waitForMessage(DataType& result)
 106     {
 107         MessageQueueWaitResult exitReason = waitForMessageFilteredWithTimeout(result, MessageQueue<DataType>::alwaysTruePredicate, infiniteTime());
 108         ASSERT(exitReason == MessageQueueTerminated || exitReason == MessageQueueMessageReceived);
 109         return exitReason == MessageQueueMessageReceived;
 110     }
 111
 112     template<typename DataType>
 113     template<typename Predicate>
 114     inline MessageQueueWaitResult MessageQueue<DataType>::waitForMessageFilteredWithTimeout(DataType& result, Predicate& predicate, double absoluteTime)
 115     {
 116         MutexLocker lock(m_mutex);
 117         bool timedOut = false;
 118
 119         DequeConstIterator<DataType> found = m_queue.end();
 120         while (!m_killed && !timedOut && (found = m_queue.findIf(predicate)) == m_queue.end())
 121             timedOut = !m_condition.timedWait(m_mutex, absoluteTime);
 122
 123         ASSERT(!timedOut || absoluteTime != infiniteTime());
 124
 125         if (m_killed)
 126             return MessageQueueTerminated;
 127
 128         if (timedOut)
 129             return MessageQueueTimeout;
 130
 131         ASSERT(found != m_queue.end());
 132         result = *found;
 133         m_queue.remove(found);
 134         return MessageQueueMessageReceived;
 135     }
 136
 137     template<typename DataType>
 138     inline bool MessageQueue<DataType>::tryGetMessage(DataType& result)
 139     {
 140         MutexLocker lock(m_mutex);
 141         if (m_killed)
 142             return false;
 143         if (m_queue.isEmpty())
 144             return false;
 145
 146         result = m_queue.first();
 147         m_queue.removeFirst();
 148         return true;
 149     }
 150
 151     template<typename DataType>
 152     inline bool MessageQueue<DataType>::isEmpty()
 153     {
 154         MutexLocker lock(m_mutex);
 155         if (m_killed)
 156             return true;
 157         return m_queue.isEmpty();
 158     }
 159
 160     template<typename DataType>
 161     inline void MessageQueue<DataType>::kill()
 162     {
 163         MutexLocker lock(m_mutex);
 164         m_killed = true;
 165         m_condition.broadcast();
 166     }
 167
 168     template<typename DataType>
 169     inline bool MessageQueue<DataType>::killed() const
 170     {
 171         MutexLocker lock(m_mutex);
 172         return m_killed;
 173     }
 174 } // namespace WTF
 175
 176 using WTF::MessageQueue;
 177 // MessageQueueWaitResult enum and all its values.
 178 using WTF::MessageQueueWaitResult;
 179 using WTF::MessageQueueTerminated;
 180 using WTF::MessageQueueTimeout;
 181 using WTF::MessageQueueMessageReceived;
 182
 183 #endif // MessageQueue_h